1. Field of the Invention
The present invention relates to an apparatus and method for generating an internal voltage adaptively from an external voltage, and more particularly, to an apparatus and method for generating an internal voltage adaptively from an external voltage supplied from a mobile terminal to supply an operating voltage to a smart card installed in the mobile terminal.
2. Description of the Related Art
Smart cards are plastic cards which include a microprocessor and a memory and thus can store and process information therein. Typically, the size and shape of a smart card are the same as those of a general credit card. A smart card, which is inserted into a mobile terminal based on the Global System for Mobile Communication (GSM) adopted in Europe, has a very small size.
In the field of mobile communications, smart cards have been widely used both as an ID card for identifying a subscriber and a card for processing billing information such as an electronic bill throughout most European countries. Smart cards are classified according to the types of networks in which they are used. In the GSM environment, a Subscribed Identify Module (SIM) card that has a subscriber authentication function and a roaming function is standard. Accordingly, a service provider issues a SIM card to a subscriber, and the subscriber who holds the SIM card can freely use communication services through any mobile terminal anywhere and at any time.
A smart card requires a constant voltage to operate its circuits. Typically, a smart card for use in a mobile terminal uses the battery of the mobile terminal as its power source.
Mobile terminals operating in the GSM environment must satisfy the GSM standard which defines the amount of power consumption, and thus, smart cards for a mobile terminal must operate according to the GSM standard. Accordingly, it is necessary to generate an internal constant voltage adaptively from a voltage supplied. Also, in the case of a smart cart in which a crypto engine is added for security enhancement, the power consumption of the crypto engine must be reduced to increase its operating speed while satisfying the GSM standard.
Since a conventional smart card for a mobile terminal uses an internal constant voltage, current can be over-consumed in a low voltage operation mode, which in turn may limit the driving speed of the crypto engine. Therefore, it is desired to control the amount of current consumption, to meet the GSM standard, and/or improve the performance of the smart card.